The present invention relates to a fuel injector.
U.S. Pat. No. 4,946,107 describes an electromagnetically operable fuel injector having, inter alia, a nonmagnetic sleeve as the connecting part between a core and a valve seating body. With its two axial ends, the sleeve is fixedly connected to the core and to the valve seating body. The sleeve runs over its entire axial length with a constant outside diameter and a constant inside diameter and accordingly has equally large inlet openings at both ends. The core and the valve seating body are designed with an outside diameter such that they extend into the sleeve at both ends so that the sleeve completely surrounds both parts, the core and the valve seating body, in areas projecting into them. A valve needle with an armature that is guided through the sleeve moves inside the sleeve. The fixed connections of the sleeve to the core and the valve seating body are achieved by welding, for example. The volume and the weight of the fuel injector can be reduced with the help of the tubular sleeve.
Unexamined German Patent No. 195 47 406 describes a fuel injector having an elongated, thin-walled, nonmagnetic sleeve which also has a bottom section in addition to its jacket section. The bottom section runs largely perpendicular to the otherwise axial extent of the sleeve along the longitudinal axis of the valve. A valve needle can move axially in a through-hole in the sleeve. A valve closing body fixedly connected to the valve needle works together with a valve seat face provided on a valve seating body, with the valve seating body pressed in the sleeve in direct or indirect contact with a bottom section of the sleeve by means of a perforated disk. In addition to the axially movable valve needle and the valve seating body, a tubular core designed as a rotating part which functions as an internal pole is arranged in the through-hole of the sleeve. The core is fixedly connected to the sleeve by welding in a desired position. A similar arrangement of a tubular core in a valve sleeve is also described in Unexamined German Patent No. 197 42 590.
Such magnetic cores which function as an internal pole for fuel injectors are usually produced by metal cutting methods, the conventional methods of producing these magnetic cores including turning, milling, drilling and precision working procedures.
A fuel injector according to the present invention has the advantage that it can be produced and installed very easily. Rolling and bending are comparatively simple and inexpensive manufacturing methods with a relatively low cost for materials.
The internal pole is manufactured from a simple metal strip in an advantageous manner. A longitudinal slot running axially on the internal pole is obtained by rolling this strip, yielding a further reduction in eddy currents and thus a greater efficiency of the magnetic circuit.
In addition, assembly of the internal pole in the valve sleeve and the stroke setting are greatly simplified with the help of the internal pole. From the beginning, the internal pole is under a radial bias after rolling and bending, allowing the internal pole to be secured easily in the valve sleeve. In addition, the radial size of the internal pole can be varied slightly due to its longitudinal slot, so that burrs are prevented from developing when the internal pole is pushed into the valve sleeve in an advantageous manner.
It is similarly easy to push the internal pole with an adjusting tool for setting the stroke of a valve needle in the valve sleeve. Therefore, the valve sleeve advantageously has a shoulder near the internal pole so that the adjusting tool can act on this shoulder just as on the internal pole.
In this way, a frictional connection can be established between the valve sleeve and the internal pole.